Skip stack_start_aligned for immediate-abort
This improves startup performance by 16%, shown by an optimized hello-world program. glibc's `pthread_getattr_np` performs expensive syscalls when reading `/proc/self/maps`. That is all wasted with `panic = immediate-abort` active because `init()` immediately discards the return value from `install_main_guard()`. A similar improvement can be seen in environments that don't have `/proc`. This change is safe because the immediately succeeding comment says that we rely on Linux's "own stack-guard mechanism".
Tracking issue: https://github.com/rust-lang/rust/issues/147286
# Benchmark
Set it up with `cargo new hello-world2`, and replace these files:
```toml
# Cargo.toml
cargo-features = ["panic-immediate-abort"]
[package]
name = "hello-world"
version = "0.1.0"
edition = "2024"
[profile.release]
lto = true
panic = "immediate-abort"
codegen-units = 1
opt-level = "z"
strip = true
# .cargo/config.toml
[unstable]
build-std = ["std"]
```
## Before
```console
home@daniel-desktop3:~/CLionProjects/hello-world2$ hyperfine -N target/release/hello-world2
Benchmark 1: target/release/hello-world2
Time (mean ± σ): 524.8 µs ± 65.1 µs [User: 276.1 µs, System: 187.0 µs]
Range (min … max): 446.4 µs … 975.5 µs 3996 runs
home@daniel-desktop3:~/CLionProjects/hello-world2$ hyperfine -N target/release/hello-world2
Benchmark 1: target/release/hello-world2
Time (mean ± σ): 519.4 µs ± 65.8 µs [User: 282.1 µs, System: 177.7 µs]
Range (min … max): 443.2 µs … 830.5 µs 3612 runs
home@daniel-desktop3:~/CLionProjects/hello-world2$ hyperfine -N target/release/hello-world2
Benchmark 1: target/release/hello-world2
Time (mean ± σ): 520.0 µs ± 64.3 µs [User: 277.1 µs, System: 182.1 µs]
Range (min … max): 447.1 µs … 1001.3 µs 3804 runs
```
For a visualization of the problem, run `cargo +stage1 build --release && perf record --call-graph dwarf -F max ./target/release/hello-world2 && perf script | inferno-collapse-perf | inferno-flamegraph > flamegraph.svg`:
<img width="3832" height="1216" alt="flamegraph with 17.41% __pthread_getattr_np" src="https://github.com/user-attachments/assets/acc2286e-1582-4772-9e3b-68b5c35e3e70" />
## After
```console
home@daniel-desktop3:~/CLionProjects/hello-world2$ hyperfine -N target/release/hello-world2Benchmark 1: target/release/hello-world2
Time (mean ± σ): 444.7 µs ± 57.3 µs [User: 257.4 µs, System: 130.2 µs]
Range (min … max): 379.4 µs … 1289.3 µs 3893 runs
Warning: Statistical outliers were detected. Consider re-running this benchmark on a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.
home@daniel-desktop3:~/CLionProjects/hello-world2$ hyperfine -N target/release/hello-world2
Benchmark 1: target/release/hello-world2
Time (mean ± σ): 452.3 µs ± 60.7 µs [User: 261.5 µs, System: 133.5 µs]
Range (min … max): 374.9 µs … 1512.4 µs 4177 runs
Warning: Statistical outliers were detected. Consider re-running this benchmark on a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.
home@daniel-desktop3:~/CLionProjects/hello-world2$ hyperfine -N target/release/hello-world2
Benchmark 1: target/release/hello-world2
Time (mean ± σ): 441.2 µs ± 56.1 µs [User: 256.2 µs, System: 128.8 µs]
Range (min … max): 375.0 µs … 760.4 µs 4032 runs
```
docs(fs): Clarify That File::lock Coordinates Across Processes
### Summary:
The documentation for `lock`, `lock_shared`, `try_lock`, and `try_lock_shared` did not make it clear that these are OS level file locks that coordinate access across processes, not just between handles within the current process.
Add "in this or any other process" to each method's existing description to clarify this.
Fixesrust-lang/rust#153618
r? @Mark-Simulacrum
std: move `sys::pal::os` to `sys::paths`
Part of rust-lang/rust#117276.
After rust-lang/rust#150723, rust-lang/rust#153130, rust-lang/rust#153341 and rust-lang/rust#153413, `sys::pal::os` only contains default-path related functions (like `getcwd` and the `PATH`-splitting logic). In line with rust-lang/rust#117276, this PR thus moves all these implementations into a new module in `sys`: `sys::paths`.
~There is one functional change here: The `chdir` implementation on SGX used to use `sgx_ineffective` which silently fails, but now returns an error unconditionally – I think that's much more reasonable given that SGX doesn't support filesystem stuff at all.~
I've corrected the misleading panic messages in `temp_dir` for UEFI and WASI, aside from that, this PR only consists of code moves.
CC @jethrogb @raoulstrackx @aditijannu for the SGX change (resolved)
Move `freeze_*` methods to `OpenOptionsExt2`
Move the unstable `freeze_last_access_time` and `freeze_last_write_time` from `OpenOptionsExt` to a new `OpenOptionsExt2` trait. This should fixrust-lang/rust#153486.
Fix environ on FreeBSD with cdylib targets that use -Wl,--no-undefined .
Instead of relying on the linker to find the 'environ' symbol, use dlsym. This fixes using `environ` from cdylibs that link with `-Wl,--no-undefined` .
Fixesrust-lang/rust#153451
Sponsored by: ConnectWise
`std`: include `dlmalloc` for all non-wasi Wasm targets
Currently, building std for a custom Wasm target with an OS other than `unknown` will fail, because `sys/alloc/mod.rs` will attempt to use `sys/alloc/wasm.rs`, the dlmalloc-based allocator used on `wasm32-unknown-unknown`. However, currently dlmalloc is only pulled in when `target_os = "unknown"`.
Instead, we should make `Cargo.toml` and `alloc/mod.rs` match: either
- disable `wasm.rs` in `alloc/mod.rs` where `not(target_os = "unknown")`, or
- pull in `dlmalloc` for all Wasm targets with `target_family = "wasm32"` that aren't covered by the [upper branches of `alloc/mod.rs`](https://github.com/rust-lang/rust/blob/main/library/std/src/sys/alloc/mod.rs#L72-L100).
This PR takes the latter approach, because it allows more code to compile without a custom allocator.
Allow passing `expr` metavariable as `cfg` predicate
This PR allows expanding `expr` metavariables inside the configuration predicates of `cfg` and `cfg_attr` invocations.
For example, the following code will now compile:
```rust
macro_rules! mac {
($e:expr) => {
#[cfg_attr($e, inline)]
#[cfg($e)]
fn func() {}
#[cfg(not($e))]
fn func() {
panic!()
}
}
}
mac!(any(unix, feature = "foo"));
```
There is currently no `macro_rules` fragment specifier that can represent all valid `cfg` predicates. `meta` comes closest, but excludes `true` and `false`. By fixing that, this change makes it easier to write declarative macros that parse `cfg` or `cfg_attr` invocations, for example https://github.com/rust-lang/rust/pull/146281/.
@rustbot label T-lang needs-fcp A-attributes A-cfg A-macros
This improves startup performance by 16%, shown by an optimized
hello-world program. glibc's `pthread_getattr_np` performs expensive
syscalls when reading `/proc/self/maps`. That is all wasted with
`panic = immediate-abort` active because `init()` immediately discards
the return value from `install_main_guard()`. A similar improvement can
be seen in environments that don't have `/proc`. This change is safe
because the immediately succeeding comment says that we rely on Linux's
"own stack-guard mechanism".
two smaller feature cleanups
Remove an unneeded feature gate for a private macro and sort the used features correctly by whether they are language or library features.
Add is_disconnected functions to mpsc and mpmc channels
Add `is_disconnected()` functions to the `Sender` and `Receiver` of both `mpmc` an `mpsc` channels.
```rust
std::sync::mpmc::Sender<T>::is_disconnected(&self) -> bool
std::sync::mpmc::Receiver<T>::is_disconnected(&self) -> bool
std::sync::mpsc::Sender<T>::is_disconnected(&self) -> bool
std::sync::mpsc::Receiver<T>::is_disconnected(&self) -> bool
```
The `mpsc` methods are locked behind the `mpsc_is_disconnected` feature gate, which has no tracking issue yet.
ACP: https://github.com/rust-lang/libs-team/issues/748
Tracking issue: https://github.com/rust-lang/rust/issues/153668
Fix bootstrap rust build failure for vxworks
Fixesrust-lang/rust#153332
Starting with VxWorks 25.09, struct stat was updated to use struct timespec instead of time_t for timestamp fields.
The following changes were made in libc in the commit [libc](https://github.com/rust-lang/libc/pull/4781).
As a result, when performing a bootstrap build with VxWorks ≥ 25.09, libc no longer exposes the fields st_mtime, st_atime, and st_ctime, as they are conditionally compiled in src/vxworks/mod.rs here [libc](https://github.com/rust-lang/libc/blob/56caa81b6b433c49c5704bf0400a02d428cfacda/src/vxworks/mod.rs#L229). This causes the build to fail.
For VxWorks versions earlier than 25.09, the build completes successfully without errors.
This PR resolves the issue by detecting the WIND_RELEASE_ID environment variable (which is set in the VxWorks build environment) and conditionally guarding the affected functions in the two additional files where the errors originate.
std: make `OsString::truncate` a no-op when `len > current_len`
Align `OsString::truncate` (and the underlying WTF-8 implementation) with `String::truncate` by making it a no-op when `len > self.len()`.
Previously, `OsString::truncate` would panic if `len > self.len()`, while `String::truncate` treats such cases as a no-op.
Tracking (`os_string_truncate`): https://github.com/rust-lang/rust/issues/133262
See also: https://github.com/rust-lang/rust/pull/32977
cc: @alexcrichton, @lolbinarycat
- `From<T> for ThinBox<T>`
- `From<T> for UniqueRc<T>`
- `From<T> for UniqueArc<T>`
- `From<T: UnwindSafe> for AssertUnwindSafe<T>`
- `From<T> for LazyCell<T, F>`
- `From<T> for LazyLock<T, F>`
Currently, building std for a custom Wasm target with an OS other than `unknown` will fail, because `sys/alloc/mod.rs` will attempt to use `sys/alloc/wasm.rs`, the dlmalloc-based allocator used on `wasm32-unknown-unknown`. However, currently dlmalloc is only pulled in when `target_os = "unknown"`.
Instead, we should make `Cargo.toml` and `alloc/mod.rs` match: either
- disable `wasm.rs` in `alloc/mod.rs` where `not(target_os = "unknown")`, or
- pull in `dlmalloc` for all Wasm targets with `target_family = "wasm32"` that aren't covered by the [upper branches of `alloc/mod.rs`](https://github.com/rust-lang/rust/blob/main/library/std/src/sys/alloc/mod.rs#L72-L100).
This PR takes the latter approach, because it allows more code to compile without a custom allocator.
std: organise `sys::pal::os`
Continuing rust-lang/rust#153341, this moves around some functions in `sys::pal`, so that `pal::os` only contains standard-path-related code (which I'll move later as part of rust-lang/rust#117276).
Best reviewed commit-by-commit.
std: add wasm64 to sync::Once and thread_parking atomics cfg guards
When targeting `wasm64-unknown-unknown` with atomics enabled, `std::sync::Once` and `thread_parking` fall through to the `no_threads`/`unsupported` implementations because the cfg guards only check for `wasm32`. This causes worker threads to panic with `unreachable` at runtime. The underlying futex implementations already handle both wasm32 and wasm64 correctly, only the cfg guards were missing wasm64.
I tested this manually with a multithreaded wasm64 application ([o1js](https://github.com/o1-labs/o1js/)) compiled with `-Z build-std=panic_abort,std` and `-C target-feature=+atomics,+bulk-memory,+mutable-globals`
Related: rust-lang/rust#83879rust-lang/rust#77839
Happy to adjust anything based on feedback
Update path separators to be available in const context
Tracking issue: rust-lang/rust#153106
This makes platform-dependent secondary path separators available in const context (ie. at compile time). The platform definitions have also been consolidated behind a common macro to prevent transcription errors, whereas previously they were defined 3-4 times per platform.
### Questions
I've manually verified that this compiles against each platform. It seems like no unit tests should be required for this change; is that correct?
* consolidate various representations of separators in std::sys::path
into a single macro_rules invocation per platform to save
transcription errors
* make `std::path::is_separator()` const
* new constants `std::path::{SEPARATORS, SEPARATORS_STR}`
std: refactor Xous startup code
To facilitate rust-lang/rust#117276 I'm moving all non-path-related code out of `sys::pal::os` (see also rust-lang/rust#153130). This is particularly involved for Xous as `pal::os` also contains the `_start` entry function and the parameter block handling. This PR moves both out into the main `sys::pal` module and also simplifies the parameter block initialisation code slightly.
CC @xobs
update panicking() docs for panic=abort
fixesrust-lang/rust#151458
The documentation for `std::thread::panicking()` has not been changed since v1.0, even though panic hooks were added in v1.10.
Current documentation is misleading for `panic=abort`
`panicking()` can return `true` in 2 different cases:
1. Thread unwinds due to panic
2. Panic hook is executing with `panic=abort`
r? @SpriteOvO
bors